In a control of change-over from a two to a four-wheel drive mode, conventional practice is to restore the drive mode from the two-wheel drive mode to the four-wheel drive mode when there is no tendency for all the wheels to be locked, after the drive mode has been changed from the four-wheel drive mode to the two-wheel drive mode.
Some of the operators or drivers may be accelerating while braking in vehicles equipped with an automatic transmission. In such a case, in spite of a desire to restore the drive mode from the two-wheel drive mode to the four-wheel drive mode, the restoration cannot be achieved when there is a locking tendency produced in the wheels which are driven wheels in the two-wheel drive mode.